Do 3-Year-Olds Receive the Same Flu Vaccine as Adults?
Yes, 3-year-olds receive the same 0.5 mL dose volume of influenza vaccine as adults, using the same standard-dose formulations. 1
Dose Volume for 3-Year-Olds
Children aged 36 months (3 years) and older receive 0.5 mL per dose of inactivated influenza vaccine (IIV), which is identical to the adult dose volume. 1
This applies to all standard-dose IIV formulations available, including Afluria, Fluarix, Flucelvax, FluLaval, and Fluzone. 1
The 0.5 mL dose contains 15 μg of hemagglutinin (HA) per vaccine virus strain (45 μg total for trivalent vaccines). 1
Critical Age Cutoff
The key distinction occurs at 36 months of age, which separates younger children who may receive smaller doses from those who receive adult-equivalent doses:
Children 6 through 35 months: Some vaccines are approved at 0.25 mL dose volumes (containing 7.5 μg HA per strain), while others use 0.5 mL even in this younger age group. 1
Children ≥36 months (≥3 years) through adults: All receive the standard 0.5 mL dose containing 15 μg HA per strain. 1
Same Vaccine Products
3-year-olds can receive the same vaccine products as adults, with important exceptions:
Standard-dose vaccines (Afluria, Fluarix, Flucelvax, FluLaval, Fluzone): Approved for ages ≥6 months through all adult ages at 0.5 mL dose for those ≥36 months. 1
High-dose vaccine (Fluzone High-Dose): Licensed ONLY for adults ≥65 years, NOT for 3-year-olds. 1, 2
Adjuvanted vaccine (Fluad): Licensed ONLY for adults ≥65 years, NOT for 3-year-olds. 1, 2
Administration Details
Route: Intramuscular (IM) injection. 1
Site for 3-year-olds: The deltoid muscle is preferred for older children, though the anterolateral thigh can also be used for younger children. 1
Site for adults: Deltoid muscle is the preferred site. 1
Number of Doses Required
While the dose volume is the same, the number of doses differs based on vaccination history:
3-year-olds who have received fewer than 2 doses of influenza vaccine previously: Require 2 doses administered ≥4 weeks apart. 1, 3
3-year-olds who have received ≥2 doses of influenza vaccine previously: Require only 1 dose per season. 1, 3
Adults: Require only 1 dose per season regardless of prior vaccination history. 4
Common Pitfall to Avoid
If a smaller 0.25 mL dose is inadvertently administered to a 3-year-old, the remaining 0.25 mL should be administered during the same visit, or a full 0.5 mL dose should be given as soon as possible if the error is discovered later. 1 This is a critical error to recognize and correct, as underdosing may result in inadequate immune response.